California Code, Public Resources Code - PRC § 5132

Under such limitations and restrictions as are prescribed by law, boards of supervisors may place in the custody and control of the county historical society, or its trustees or other directors, any records, landmarks, or other property, real or personal, of the county having only historical value.  The trustees and directors shall at all times be appointed by the historical society with the consent and approval of the board of supervisors and shall not receive compensation from the county.  The board of supervisors may prescribe reasonable conditions for the delivering of the property.